That's exactly why you want NAT/firewalling and other existing mechanisms.
These are devices that do not require global addressability. In fact they
SHOULD NOT be globally addressable.
first, don't confuse NAT with firewalls. they have entirely separate
functions which often happen to be provided in the same box. NAT provides
very little additional security by itself, and you can implement any
firewall function without doing address translation.
second, firewalls are not a general-purpose security mechanism. at best
they are a means of decreasing the effort required to analye potential
security threats. they are not a substitute for implementing security
at the end system.
third, it seems quite presumptious for you to declare that someone else's
device or application does not, or should not, require global addressability.
in fact there are numerous cases where global addressability is desirable.
the needs of the network are more diverse than your security model can
accomodate.
IPv6 needs to be justified on the number of nodes that truly need a
globally accessible public address, not by insisting on counting devices
that should remain anonymous or under limited (and controlled) visibility.
you appear to be confusing visibility with accessibility.
At times I suspect an administrative standard for uniquely referring
to a private IP address is a specific private IP network would have
been the only required improvement in global addressing.
that's because you aren't bothering to consider the needs of applications.
Keith